Measuring instrument



Patented Dec. 27, 1922'.

UNITED STATES PATENT OFFICE.

DUNCAN DUNN IN G, 01 BERKELEY, CALIFORNIA, ASSIGNOR TO THE GOVERNMENT AND THE PEOPLE OF THE UNITED STATES.

MEASURING INSTRUMENT.

Application filed January 28, 1927. Serial No. 164,335.

(GRANTED UNDER THE ACT OF MARCH 3, 1883; 22 STAT. L. 625.)

This application ismade under the act of March 3, 1883, chapter 143 (22 Stat. 625) and the invention herein described and claimed may be used by the Government of the United States or any of its officers or employees in the prosecution of work for the Government, or by any other person in the United States, without payment to me of any royalty thereon.

The main object of the'instrument is to provide a ruler for measuring the width of the annual growth rings of trees from cores obtained by the use 01" a Swedish increment borer. The borer, when screwed into a tree, along a radius and perpendicular to the pith, cuts a core approximately or ,4 inch in diameter and of a length dependent upon the size of the tree, length of the borer and the wishes of the user. Each annual growth ring of the tree appears as a lamination, perpendicular to the length of the core.

My instrument makes provision for holding said cores removed from the trees; for trimming said cores to render the growth rings more distinct along the radius; for n'icasuring the width of said annual rings or groups of rings; for doubling said measurements along the radius to give the corresponding measurement along the diameter; and for magnifying both core and scale for increas-iing accuracy.

The invention is shown in the accompany ing drawing, which is in two figures; Fig.1 1 is a plan view of the measuring instrument with certain parts broken away. Fig. 2 is an end sectional view of the same.

Referring to the drawing, it will be seen that the instrument consists of two blocks 1 and 2 of wood 'or other material, provided with a bolt 3 equipped with a thumb-brad 3" for holding the blocks firmly together. Springs 4: are provided for separating the blocks 1 and 2 when the clamping device 3 is loosened to permit insertion or removal of the tree core that it is intended to measure.

Guide pins 5 or other suitable means are provided for holding the blocks 1 and 2 in the desired alignment when clamped together or separated. These pins 5 carry springs 4 and work in aligning bores in the rule. A groove 6 of circular cross section pendicular to the increment core. pose of the indicator 13 to align by means of extends along the upper faces of the blocks 1 and 2 with its axis lying in the plane of contact between the two blocks. Said groove should be of the size necessary to produce firm contact with the increment core when the clamping devices are closed thereon. In addition the axis of said grooveis to he so located that a portion of thesai'd core shall project above the upper faces of said blocks to permit trimming the said core with an edge tool to render the growth rings more distinct. To facilitate this trimming operation, plates 6*, lying in the same plane, are provided on the upper surfaces of the two blocks, thereby furnishing a bearing surface for an edge tool such'as a knife, razor blade or chisel used for trimming the core, said plates to bear one or more scales 7 for measuring the width of the growth rings. Said scales may be in any desired units, and may include a scale indicating double the actual distances for automatically converting width of rings along a radius into the corresponding width along a diameter. Grooves 8 are provided near the upper edge of the outer face of each of the blocks 1 and 2 for using a standard slide rule runner 9, or other indicating device, consisting of a piece of glass with a line etched thereon per- The purthe line thereon, the position of the annual rings with the scale or scales for measure ment.

I claim: v

.A ruler of the character described, including an elongated body portion comprising two blocks, each block having a groove extending longitudinally thereof, said grooves, when the blocks are brought in contact with each other, forming a single groove adapted to receive the object to be measured, means for holding said blocks in close contact or in spaced relation to each other as may be desired, aligning means for said blocks, plates atiixed to the upper faces of said blocks, said plates having a scale etched thereon and extending adjacent the grooves in said blocks, and a rule indicator adapted to slideon said blocks.

DUNCAN DUNNING. 

